The main task of distributed generators in a microgrid is to deliver maximum real power to meet load demands. The system voltage is typically maintained by the main grid, to which it is connected. However, in weak grid and off grid operation, reactive power support from the distributed generators is required in many cases.
Various centralized control approaches for assigning real and reactive power references have been investigated.
EP 1933441 A1 discloses a system for controlling a microgrid including microgrid assets and a tieline for coupling the microgrid to a bulk grid; and a tieline controller coupled to the tieline. At least one of the microgrid assets comprises a different type of asset than another one of the microgrid assets. The tieline controller is configured for providing tieline control signals to adjust active and reactive power in respective microgrid assets in response to commands from the bulk grid operating entity, microgrid system conditions, bulk grid conditions, or combinations thereof.
EP 2518853 A1 discloses systems, methods, and apparatus for providing coordinated volt/VAR control in power distribution networks. According to an example embodiment of the invention, a method is provided for coordinating voltage and volt-amps-reactive (VAR) control (VVC) in power distribution networks. The method can include receiving one or more VVC objective functions from a distribution management system; determining at least one microgrid conservation voltage reduction factor (CVRF); forecasting microgrid load profile for a predetermined period of time; controlling microgrid VVC resources based at least on the one or more received VVC objective functions; and communicating the at least one microgrid CVRF and the forecasted load profile to the distribution management system.